Peptide derivatives

ABSTRACT

This invention relates to peptide derivatives of the formula ##STR1## or salts thereof, wherein: (a) Q 1  represents a 1-dimethylamino-2-methylpropyl group and Q 2  represents an (R)- or (S)-2-hydroxy-2-phenylethylamino group, a 2-phenylcyclopropylamino group or a 1,2,3,4-tetrahydroisoquinolin-2-yl group, or 
     (b) Q 1  represents a 1-methyl-2-pyrrolidinyl group and Q 2  represents ##STR2##

This application is a 371 of PCT/JP96/00949 filed Apr. 8, 1996.

TECHNICAL FIELD

This invention relates to novel peptide derivatives having an antitumoractivity and, more particularly, to peptide derivatives of the formula##STR3## or salts thereof, wherein: (a) Q₁ represents a1-dimethylamino-2-methylpropyl group and Q₂ represents an (R)- or(S)-2-hydroxy-2-phenylethylamino group, a 2-phenylcyclopropylamino groupor a 1,2,3,4-tetrahydroisoquinolin-2-yl group, or

(b) Q₁ represents a 1-methyl-2-pyrrolidinyl group and Q₂ represents##STR4## where A represents a hydrogen atom or ##STR5## in which Yrepresents a hydrogen atom or --COR₁, and R₁ represents a hydroxylgroup, a lower alkoxy group, an aralkyloxy group or ##STR6## in which R₂and R₃ may be the same or different and each represents a hydrogen atom,a lower alkyl group, a phenyl group, or a four- to seven-memberedheterocyclic group containing one or two heteroatoms selected from S, Oand N, or R₂ and R₃, together with the nitrogen atom to which they areattached, may form a four- to seven-membered heterocyclic group whichmay further contain one heteroatom selected from S, O and N, and

B represents a phenyl group which may optionally be substituted by ahalogen atom, hydroxyl group, lower alkyl group or lower alkoxy group.

BACKGROUND ART

Up to now, several compounds having a cell growth inhibiting activityand/or an antineoplastic activity have been isolated from a marinemollusk (Dolabella auricularia) which is akin to the sea hare, and thesecompounds are called dolastatins 1-15. Among them, dolastatin 10 is apentapeptide extracted from the Indian Ocean (sea hare Dolabellaauricularia) by Pettit in 1987 and having the structural formula givenbelow, and is known to be a compound having the most powerful cellgrowth inhibiting activity of all the existing compounds (see Pettit etal., Journal of the American Chemical Society, Vol. 109, p. 6883, 1987and U.S. Pat. No. 4,816,444). ##STR7##

Thereafter, the total synthesis of dolastatin 10 was also reported (seeU.S. Pat. No. 4,978,744).

Meanwhile, the present inventors previously disclosed certainderivatives of dolastatin 10 (see the pamphlets of WO 93/03054 and WO95/09864).

Now, the present inventors have found that (a) certain derivatives ofdolastatin 10 obtained by replacing the dolaphenineα-(thiazoly)phenethylamine! located at the C-terminus of dolastatin 10by another substituent group and (b) certain derivatives of dolastatin10 obtained by replacing the dolavaline (N,N-dimethylvaline) located atthe N-terminus of dolastatin 10 by N-methylproline have a far morepowerful antitumor activity than dolastatin 10.

DISCLOSURE OF THE INVENTION

The term "lower" as used herein means that the groups or compoundsmodified by this term have not more than six carbon atoms and preferablynot more than four carbon atoms.

In the above formula (I), examples of the "lower alkyl group" includemethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl and n-hexyl groups, and examples of the "lower alkoxy group"include methoxy, ethoxy, n-propoxy, isopropoxy and n-butoxy groups.Moreover, the "aralkyloxy group" means an aryl-(lower alkyl)oxy group,and examples thereof include benzyloxy and phenetyloxy. The "halogenatoms" include fluorine, chlorine, bromine and iodine atoms.

When R₂ or R₃ represents "a four- to seven-membered heterocyclic groupcontaining one or two heteroatoms selected from S, O and N," examples ofthe heterocyclic group include azetidinyl, furyl, thienyl, pyridyl,piperidinyl, azepinyl, thiazolyl, imidazolyl, oxazolyl, pyrimidinyl andpyridazinyl groups. On the other hand, when R₂ and R₃, together with thenitrogen atom to which they are attached, form a four- to seven-memberedheterocyclic group which may further contain one heteroatom selectedfrom S, O and N," examples of the heterocyclic group include azetidino,pyrrolidino, piperidino, 1-perhydroazepinyl, piperazino, morpholino, andthiomorpholino groups.

Thus, examples of the group ##STR8## include amino, methylamino,ethylamino, isopropylamino, tert-butylamino, dimethylamino,diethylamino, phenylamino, N-methyl-N-phenylamino, furylamino,pyridylamino, 2-thiazolylamino, imidazolylamino, pyrimidylamino,pyrrolidino, piperidino and morpholino groups.

The "phenyl group which may optionally be substituted by a halogen atom,hydroxy group, lower alkyl group or lower alkoxy group"as represented bythe symbol B means an unsubstituted phenyl group or a phenyl groupsubstituted by one halogen atom, hydroxy group, lower alkyl group orlower alkoxy group, and examples thereof include phenyl, 2-fluorophenyl,2-chlorophenyl, 2-bromophenyl, 3-fluorophenyl, 3-iodophenyl,4-fluorophenyl, 4-chlorophenyl, 4-bromophenyl, 2-hydroxyphenyl,4-hydroxyphenyl, 2-methylphenyl, 4-ethylphenyl, 2-methoxyphenyl and4-ethoxyphenyl.

A group of preferred compounds in accordance with the present inventionare the compounds of the above formula (I) wherein Q₁ represents a1-dimethylamino-2-methylpropyl group and Q₂ represents an (R)- or(S)-2-hydroxy-2-phenylethylamino group.

Another group of preferred compounds in accordance with the presentinvention are the compounds of the above formula (I) wherein Q₂represents ##STR9## where A is a hydrogen atom and B is a phenyl groupwhich may optionally be substituted by a halogen atom (in particular, afluorine atom).

Still another group of preferred compounds in accordance with thepresent invention are the compounds of the above formula (I) wherein Q₂represents ##STR10## in which A is a 2-thiazolyl group which mayoptionally be substituted by an N-(lower alykyl)carbamoyl group, and Bis an unsubstituted phenyl group.

In the compounds of the above formula (I) in accordance with the presentinvention, the carbon atoms to which an isopropyl, sec-butyl, methoxy ormethyl group is attached are asymmetric carbon atoms and can hence haveany (R)- or (S)-steric configuration. Although all such compounds arewithin the scope of the present invention, compounds having the samesteric configuration as dolastatin 10 are preferred from the viewpointof pharmacological activity.

The peptide compounds of the above formula (I) can also exist in theform of salts. Examples of such salts include hydrochlorides,hydrobromides, trifluoroacetates, p-toluenesulfonates and acetates.

In the practice of the present invention, the peptide compounds of theabove formula (I) may be prepared by condensing appropriate amino acidsor peptide fragments, for example, according to a liquid phase syntheticmethod (see E. Schroder and K. Lubke, "The Peptides". Vol. 1, pp.76-136, 1965, Academic Press) which is well known in the field ofpeptide chemistry.

For example, in order to avoid racemization during condensation, it issuitable to synthesize the peptide compounds by condensing a tripeptidefragment of the following formula (II) ##STR11## wherein Q₁ has the samemeaning as described previously, with a fragment of the followingformula (III) ##STR12## wherein Q₂ has the same meaning as describedpreviously.

Moreover, in order to synthesize many of the compounds of the presentinvention efficiently, it is preferable to condense a tetrapeptidefragment of the following formula (IV) ##STR13## wherein Q₁ has the samemeaning as described previously, with a fragment of the followingformula (V)

    H--Q.sub.2                                                 (V)

wherein Q₂ as the same meaning as described previously.

The condensation reactions may generally be carried out by treatmentwith a condensing agent such as dicyclohexylcarbodiimide (DOC),diphenylphosphoryl azide (DPPA), diethyl cyanophosphate (DEPC) or BOPreagent, in an inert solvet such as chloroform, ethyl acetate,tetrahydrofuran (THF), dimethylformamide (DMF) or acetonitrile, and inthe presence of an organic base such as triethylamine,N-methylmorpholine or diisopropylethylamine (DIEA), if necessary.

The reaction temperature usually ranges from -10° C. to room temperatureand is preferably around 0° C. As to the proportions in which thecompound of formula (III), the organic base and the condensing agent areused relative to the compound of formula (II), it is advantageous to useat least 1 mole, preferably about 1.0-1.1 moles, of the compound offormula (III), about 1-2 moles of the organic base, and about 1 mole ofthe condensing agent, per mole of the compound of formula (II).

The reaction of the compound of formula (IV) with the compound offormula (V) may be carried out under the same conditions as describedabove for the reaction of the compound of formula (II) with the compoundof formula (III).

The compounds of formula (I) wherein Y is a carboxyl group may also beprepared by hydrolyzing a compound of formula (I) wherein Y is a (loweralkoxy)carbonyl group, in the presence of an alkali.

The peptide compounds of formula (I) formed in the above-describedmanner may be isolated from the reaction mixture and purified byrecrystallization, ion-exchange chromatography, gel filtration,high-performance liquid chromatography or the like.

Most of the compounds of the above formulas (II), (III) and (IV) used asstarting materials in the above-described reactions are novel compoundswhich have not hitherto been described in the literature. However, theymay readily be prepared by condensing their constituent amino acidsaccording to the liquid phase synthetic method.

The compounds of formula (I) in accordance with the present inventionhave a more powerful antitumor activity than that of dolastatin 10, andalso have high therapeutic ratios. Accordingly, they are useful for thetreatment or therapy of, for example, leukemia, non-small cell carcinomaof the lungs, small cell carcinoma of the lungs, cancer of the colon,cancer of the CNS, melanoma, ovarian carcinoma, cancer of the kidneys,cancer of the stomach, and cancer of the urinary bladder.

The antitumor activity of the compounds of formula (I) in accordancewith the present invention can be determined in the following manner.

0.1 ml (10⁶ cells per mouse) each of mouse leukemia P388 cells wastransplanted into the abdominal cavity of 7-weeks-old CDF1 mice. On thefirst day (the next day) and the fifth day after transplantation, a drugwas administered intraperitoneally and the life or death of the mice wasobserved for 60 days. Then, the percent increase in life-span (ILS) wascalculated from the results of observation according to the followingequation. In the following equation, T designates the median number ofdays for which the mice of the drug-treated group survived, and Cdesignates the median number of days for which the mice of the controlgroup survived. ##EQU1##

The results thus obtained are shown in the following table. Theantitumor activity of each drug is expressed as a relative value basedon the antitumor activity of dolastatin 10 for which ILS is regarded as1.

                  TABLE                                                           ______________________________________                                        Example No. of compound                                                                        Antitumor activity                                           ______________________________________                                        Example 1        1.5                                                          Example 2        1.9                                                          Example 9        1.3                                                          Dolastatin 10    1                                                            ______________________________________                                    

When the compounds of the present invention are used as drugs, they maybe formulated in any of various pharmaceutical preparations according tothe intended purpose. These pharmaceutical preparations include solidpreparations such as tablets, hard capsules, soft capsules, granules,powders, subtilized granules, pills and troches; semisolid preparationssuch as suppositories and ointments; and liquid preparations such asinjections, emulsions, suspensions, lotions and sprays. Non-toxicadditives which can be used in the aforesaid pharmaceutical preparationsinclude, for example, starch, gelatin, glucose, lactose, fructose,maltose, magnesium carbonate, talc, magnesium stearate, methylcellulose,carboxymethylcellulose and salts thereof, acacia, polyethylene glycol,alkyl esters of p-hydroxybenzoic acid, syrup, ethanol, propylene glycol,petrolatum, carbowax, glycerin, sodium chloride, sodium sulfite, sodiumphosphate and citric acid. The aforesaid pharmaceutical preparations mayalso contain other therapeutically effective drugs.

The content of the compounds of the present invention in the aforesaidpharmaceutical preparations may vary according to the dosage form.Generally, it is desirable that solid and semisolid preparations containthe compounds of the present invention in an amount of 0.1 to 50% byweight and liquid preparations contain them in an amount of 0.05 to 10%by weight.

The dosage of the compounds of the present invention may vary widelyaccording to the type of the warm-blooded animal (including humanbeings) to be treated, the route of administration, the severity ofsymptoms, the diagnostic judge by the doctor, and the like. Generally,they may be administered in a daily dose of about 0.01 to 50 mg/kg.However, it is a matter of course that they may be administered in dosesless than the lower limit of the aforesaid range or greater than theupper limit thereof, depending on the severity of symptoms in thepatient and the diagnostic judge by the doctor. The aforesaid daily dosemay be given at a time or in several divided doses.

EXAMPLES

The present invention is more specifically explained with reference tothe following reference examples and examples.

As to the structures of the compounds corresponding to the compoundnumbers used in the reference examples and examples, see the followingflow sheets 1 to 3. In these flow sheets, Bu^(t), Boc, Bzl, Z and Merepresent tert-butyl, tert-butoxycarbonyl, benzyl, benzyloxycarbonyl andmethyl groups, respectively. Q₂, B and Y have the same meanings asdescribed previously. ##STR14##

Reference Example 1

830.7 mg (1.71 millimoles) of compound 1 was dissolved in 20 ml of 50%trifluoroacetic acid/dichloromethane under cooling with ice. Thissolution was stirred at room temperature for 2 hours and then evaporatedto dryness under reduced pressure. After the residue was dissolved in 5ml of dimethylformamide (DMF), 2.4 ml of triethylamine was added theretounder cooling with ice and the resulting mixture was evaporated todryness under reduced pressure.

On the other hand, 644.3 mg (1.71 millimoles) of compound 2 wasdissolved in 8.6 ml of 4N hydrogen chloride/dioxane under cooling withice. This solution was stirred at room temperature for 1.5 hours andthen evaporated to dryness under reduced pressure.

Both of the above residues were combined and dissolved in 7 ml of DMF.While this solution was being stirred under cooling with ice, 352 mg(2.16 millimoles) of diethyl cyanophosphate (DEPC) and 0.53 ml (3.82millimoles) of triethylamine were added thereto and the resultingmixture was stirred overnight at temperatures ranging from 0° to roomtemperature. The reaction mixture was diluted with an ethylacetate-benzene (4:1) mixture, washed with a saturated aqueous solutionof sodium bicarbonate and a saturated aqueous solution of sodiumchloride, and then dried. After the solvent was distilled off, theremaining oily matter (1.35 g) was purified by Sephadex LH-20 columnchromatography using hexane-methanol-dichloromethane (4:5:15) as theeluent. Thus, 1.06 g of the desired compound 3 was obtained as anamorphous material (in a 89.7% yield).

α!²⁸ _(D) -48.2 ° (c=0.375, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.1(m), 1.27(3H, d, J=6.8 Hz), 1.6-2.2(m),2.25(6H, s), 2.3-2.6(m), 3.02(3H, s), 3.30(3H, s), 3.35(3H, s),3.9-4.3(m), 4.80(1H, dd, J=9.2 Hz, 6.4 Hz), 5.13(2H, s), 6.86(1H, br.d), 7.34(5H, s).

Reference Example 2

688 mg (1.00 millimole) of compound 3 was dissolved in 10 ml oft-butanol-water (9:1), and 0.1 g of 5% palladium-carbon was addedthereto. This mixture was stirred in a stream of hydrogen for 5 hours.After the catalyst was filtered off and washed, the filtrate and thewashings were combined and evaporated to dryness under reduced pressure.Thus, 590 mg of the desired compound 4 was obtained as colorless foamymaterial (in a 98.7% yield).

α!²⁸ _(D) -57.3° (c=0.955, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.1(m), 1.17 (3H, d, J=4.4 Hz), 1.6-2.2(m),2.54(6H, s), 3.04 and 3.08(3H, s), 3.27 and 3.31(3H, s), 3.36 and3.42(3H, s), 4.0-4.3(m), 4.6-5.0(m), 5.0-5.4(m), 6.97(1H, br. d).

Example 1

30 mg (50 micromoles) of compound 4 and 10 mg (58 micromoles) of(R)-2-hydroxy-2-phenylethylamine hydrochloride were dissolved in 0.5 mlof DMF. While this solution was being stirred under cooling with ice,9.5 mg (58 micromoles) of DEPC and 16 μl (11.5 micromoles) oftriethylamine were added thereto and the resulting mixture was stirredovernight at temperatures ranging from 0° to room temperature. Thereaction mixture was diluted with dichloromethane, washed with asaturated aqueous solution of sodium bicarbonate and a saturated brine,and then dried. After the solvent was distilled off, the resultingresidue was purified by preparative TLC developing solvent:dichloromethane-methanol (10:1)! and then by Sephadex LH-20 columnchromatography using hexane-methanol-dichloromethane (4:5:15) as theeluent. Thus, 25.1 mg of the desired compound 5-A (i.e., compound 5 inwhich Q is an (R)-2-hydroxy-2-phenylethylamino group) was obtained as anamorphous material (in a 69.9% yield).

α!²⁸ _(D) -43.8° (c=0.319, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.1(m), 1.27(3H, d, J=7.0 Hz), 1.6-2.2(m),2.27(6H, s), 2.3-2.6(m), 3.02(3H, s), 3.32(3H, s), 3.43(3H, s), 3.82(1H,br. d), 4.0-4.2(m), 4.77(1H, dd, J=9.0 Hz, 6.8 Hz), 6.6-7.0(m),7.2-7.5(5H, m).

Example 2

Using compound 4 and (S)-2-hydroxy-2-phenylethylamine, compound 5-B(i.e., compound 5 in which Q₂ is an (S)-2-hydroxy-2-phenylethylaminogroup) was obtained (in a 79.1% yield) in the same manner as describedin Example 1.

α!²⁸ _(D) -44.5° (c=0.330, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.1(m), 1.26(3H, d, J=7.0 Hz), 1.5-2.2(m), 2.65(6H, s), 3.02 (3H, s), 3.32 (3H, s), 3.40(3H, s), 3.85(1H, dd, J=9.5 Hz,1.5 Hz), 4.0-4.2(m), 4.71(1H, dd, J=8.1 Hz, 6.8 Hz), 4.8-5.1(m),6.7-6.9(m), 7.2-7.5(5H, m).

Example 3

Using compound 4 and dl-trans-2-phenylcyclopropylamine, compound 5-C(i.e., compound 5 in which Q₂ is a 2-phenylcyclopropylamino group) wasobtained (in a 82.1% yield) in the same manner as described in Example1.

α!²⁴ _(D) -52.4° (c=0.354, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.2(m), 1.2-1.4(m), 1.6-2.2 (m), 2.37 (6H, s),3.02 (3H, s), 3.33 and 3.35 (3H, s), 3.41(3H, s), 3.8-4.3(m), 4.76(1H,dd, J=8.7 Hz, 6.9 Hz), 7.26(5H, s).

Example 4

Using compound 4 and 1,2,3,4-tetrahydroisoquinoline, compound 5-D (i.e.,compound 5 in which Q₂ is a 1,2,3,4-tetrahydroisoquinolin-2-yl group)was obtained (in a 66.2% yield) in the same manner as described inExample 1.

α!²³ _(D) -48.2° (c=0.320, MeOH)

¹ H-NMR (CDCl₃, δ): 0.6-1.1(m), 1.1-1.3(m), 1.5-2.2(m), 2.55(6H, s),2.7-3.0(m), 3.00(3H, s), 3.30(3H, s), 3.44(3H, s), 3.55-4.0(m),4.0-4.3(m), 4.5-5.0(m), 7.15 and 7.19(4H, s).

Reference Example 3

0.85 g (1.73 millimoles) of compound 6 was dissolved in 15 ml oft-butanol-water (9:1), and 0.1 g of 5% palladium-carbon was addedthereto. This mixture was stirred in a stream of hydrogen. After 3hours' reaction, the catalyst was filtered off and washed, and thefiltrate and the washings were combined and evaporated to dryness underreduced pressure. The residue was dissolved in 20 ml of benzene, andthis solution was evaporated to dryness under reduced pressure. Thisprocedure was repeated once more to obtain oily matter. This oilymatter, together with 0.48 g (1.93 millimoles) of Z-proline and 0.31 g(1.90 millimoles) of diethyl cyanophosphate (DEPC), was dissolved in 10ml of dimethylformamide (DMF). While this solution was being stirredunder cooling with ice, a solution of 0.19 g (1.88 millimoles) oftriethylamine in 1 ml of DMF was added dropwise thereto.

Thereafter, the stirring was continued at 0° C. for 4 hours and at roomtemperature overnight. The resulting clear reaction mixture was fullydiluted with ethyl acetate, washed with ice-cold 2N hydrochloric acidand a saturated aqueous solution of sodium bicarbonate, and then dried.The solvent was distilled off under reduced pressure to obtain 1.01 g ofoily material. This oily material was purified by silica gel columnchromatography eluent: ethyl acetate-hexane (2:1)!. Thus, 0.97 g of thedesired compound 7 was obtained as a colorless foamy material (in a95.1% yield).

α!²⁷ _(D) -81.7° (c=1.025, MeOH)

¹ H-NMR (CDCl₃, δ): 0.75-1.05(12H, m), 1.46(9H, s), 1.8-2.2(4H, m),2.3-2.4(2H, m), 2.96(3H, s), 3.34(3H, s), 3.4-3.6(2H, m), 3.8-4.0(1H,m), 4.2-4.4(1H, m), 4.73(1H, dd, J=8.9 Hz, 6.3 Hz), 5.17(2H, br. s),7.32(5H, s).

Reference Example 4

0.50 g (0.85 millimole) of compound 7 was dissolved in 20 ml ofmethanol, and 1.0 g of 37% formalin and 0.4 g of 5% palladium-carbonwere added thereto. This mixture was stirred in a stream of hydrogen for48 hours. After the catalyst was filtered off and washed with methanol,the filtrate and the washings were combined and evaporated to drynessunder reduced pressure. The resulting oily material was dissolved inethyl acetate-hexane (1:1), and any insoluble material was removed byfiltration. After the filtrate was evaporated to dryness under reducedpressure, the remaining oily material was purified by silica gel columnchromatography eluent: ethyl acetate-hexane (2:1)!. Thus, 0.36 g of thedesired compound 8 was obtained as a colorless oily material (in a 90.0%yield).

α!²⁵ _(D) -76.2° (c=1.10, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.05(12H, m), 1.46(9H, s), 1.6-1.9(4H, m),2.31(3H, s), 2.3-2.45(2H, m), 2.99(3H, s), 3.36(3H, s), 3.75-4.0(1H, m),4.73(1H, dd, J=8.9 Hz, 7.1 Hz), 7.81(1H, br. d).

Reference Example 5

310 mg (0.66 millimole) of compound 8 was dissolved in 50%trifluoroacetic acid/dichloromethane at 0° C. This solution was stirredat room temperature for 1 hour and then evaporated to dryness underreduced pressure.

On the other hand, 263 mg (0.70 millimole) of compound 2 was dissolvedin 4N hydrogen chloride/dioxane at 0° C. This solution was stirred atroom temperature for 1 hour and then evaporated to dryness under reducedpressure. After the residue was dissolved in 3 ml of DMF, 0.9 ml oftriethylamine was added thereto under cooling with ice and the resultingmixture was evaporated to dryness under reduced pressure. After theseresidues were combined and dissolved in 3 ml of DMF, 136 mg (0.83millimole) of DEPC and 0.11 ml (0.79 millimole) of triethylamine wereadded thereto under cooling with ice and the resulting mixture wasallowed to stand overnight with stirring.

The reaction mixture was diluted with an ethyl acetate-benzene (4:1)mixture, washed with a saturated aqueous solution of sodium bicarbonateand a saturated brine, and then dried. After the solvent was distilledoff to obtain 449 mg of oily material. This oily material was purifiedby silica gel column chromatography eluent: dichloromethane-methanol(30:1→10:1)!. Thus, 185 mg of the desired compound 9 was obtained as acolorless oily material (in a 41.5% yield).

α!_(D) n.d.

¹ H-NMR (CDCl₃, δ): 0.7-1.1(m), 1.27(3H, d, J=7.0 Hz), 1.5-2.3(m), 2.34(3H, s), 2.3-2.9 (m), 3.00 (3H, s), 3.30(3H, s), 3.35(3H, s),3.85-4.3(m), 4.68(1H, dd, J=8.7 Hz, 4.9 Hz), 5.13(2H, s), 7.34(5H, s).

Reference Example 6

185 mg of compound 9 was dissolved in 3 ml of t-butanol-water (9:1), and40 mg of 5% palladium-carbon was added thereto. This mixture was stirredin a stream of hydrogen for 5 hours. After the catalyst was filtered offand washed, the filtrate and the washings were combined and evaporatedto dryness under reduced pressure. Thus, 155 mg of the desired compound10 was obtained as a colorless oily material (in a 97.1% yield).

α!_(D) -83.3° (c=0.365, MeOH)

Example 5

23.4 mg (40 micromoles) of compound 10 and 12.1 mg (100 micromoles) ofphenethylamine were dissolved in 0.5 ml of DMF. While this solution wasbeing stirred under cooling with ice, 9.6 mg (59 micromoles) of DEPC and8 μl of triethylamine were added thereto and the resulting mixture wasallowed to stand overnight with stirring. The reaction mixture wasdiluted with dichloromethane, washed with a saturated aqueous solutionof sodium bicarbonate and a saturated aqueous solution of sodiumchloride, and then dried. The solvent was distilled off to obtain 23.0mg of residue. This residue was purified by Sephadex LH-20 columnchromatography eluent: hexane-methanol-dichloromethane (4:5:15)!. Thus,18.8 mg of the desired compound 11-A (i.e., compound 11 in which B is aphenyl group) was obtained as a colorless waxy material (in a 68.6%yield).

α!²⁵ _(D) -61.0° (c=0.39, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.1(m), 1.21(3H, d, J=7.0 Hz), 1.5-2.2(m),2.38(3H, s), 2.83(2H, t, J=7.0 Hz), 3.01 (3H, s), 3.32(3H, s), 3.36(3H,s), 3.2-3.6(m), 3.84(1H, dd, J=7.9 Hz, 2.2 Hz), 3.9-4.2(m), 4.71(1H, dd,J=9.2 Hz, 7.0 Hz), 6.3-6.6(m), 7.23(5H, s), 7.7-8.1(1H, m).

The compounds of Examples 6-8 were obtained by reacting compound 10 withphenethylamine derivatives in the same manner as described in Example 5.

Example 6

Compound 11-B (i.e., compound 11 in which B is a 2-fluorophenyl group)was obtained as a waxy material (in a 73.0% yield).

α!²⁸ _(D) -61.7° (c=0.326, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.1(m), 1.21(3H, d, J=7.1 Hz), 1.5-2.3(m),2.33(3H, s), 2.3-2.6(m), 2.88(2H, t, J=7.3 Hz), 3.01(3H, s), 3.32(3H,s), 3.37(3H, s), 3.2-3.7(m), 3.84(1H, dd, J=8.0 Hz, 2.5 Hz),3.9-4.2(br), 4.5-4.9(1H, m), 6.4-6.6(1H, m), 6.8-7.3(4H, m), 7.6-8.1(1H,m).

Example 7

Compound 11-C (i.e., compound 11 in which B is a 3-fluorophenyl group)was obtained as an amporphous powder (in a 70.9% yield).

α!²⁸ _(D) -56.7° (c=0.287, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.1(m), 1.22(3H, d, J=7.0 Hz), 1.5-2.2(m),2.34(3H, s), 2.3-2.7(m), 2.84(2H, t, J=6.8 Hz), 3.02(3H, s), 3.32(3H,s), 3.36(3H, s), 3.3-3.6(m), 3.83(1H, dd, J=8.4 Hz, 2.2 Hz), 3.9-4.3(m),4.5-4.9(m), 6.5-6.7(1H, m), 6.8-7.2(4H, m), 7.7-8.1(1H, m).

Example 8

Compound 11-D (i.e., compound 11 in which B is a 4-fluorophenyl group)was obtained as an amorphous powder (in a 72.7% yield).

α!²⁸ _(D) -55.9° (c=0.285, MeOH)

¹ H-NMR (CDCl ₃, δ): 0.7-1.1(m), 1.22(3H, d, J=7.3 Hz), 1.5-2.2(m),2.34(3H, br. s), 2.80(2H, t, J=7.0 Hz), 3.01(3H, s), 3.32(3H, s),3.36(3H, s), 3.2-3.6(m), 3.75-3.95(1H, m), 3.95-4.3(m), 4.5-4.9(m),6.4-6.6(1H, m), 6.8-7.2(4H, m).

Example 9

0.4 ml of 50% trifluoroacetic acid/dichloromethane was added to 14.8 mg(32 micromoles) of compound 8 under cooling with ice. This mixture wasstirred at room temperature for 4 hours and then evaporated to drynessby flushing with nitrogen gas. On the other hand, 14.3 mg (30micromoles) of compound 12-A (i.e., compound 12 in which Y is a hydrogenatom) was treated with 0.4 ml of 50% trifluoroaceticacid/dichloromethane in the same manner as described above. Then, thismixture was evaporated to dryness. After both of these residues werecombined and dissolved in 1 ml of DMF, 85 μl of triethylamine was addedthereto under cooling with ice and the resulting mixture was evaporatedto dryness under reduced pressure. The resulting residue was dissolvedagain in 0.4 ml of DMF. While this solution was being stirred undercooling with ice, 6.7 mg (41 micromoles) of DEPC and 10 μl (72micromoles) of triethylamine were added thereto and the resultingmixture was allowed to stand overnight with stirring.

The reaction mixture was evaporated to dryness under reduced pressure.After the residue was dissolved in dichloromethane, this solution waswashed with a saturated aqueous solution of sodium bicarbonate and asaturated brine, and then dried. After the solvent was distilled off,the resulting residue was purified by preparative TLC developingsolvent: dichloromethanemethanol (10:1)!. Thus, 14.5 mg of the desiredcompound 13-A (i.e., compound 13 in which Y is a hydrogen atom) wasobtained as a white powder (in a 62.0% yield).

α!²⁵ _(D) -92.4° (c=0.218, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.2(m), 1.22(3H, d, J=7.0 Hz), 1.5-2.0(m), 2.35(3H, s), 3.01 (3H, s), 3.33 (3H, s), 3.36(3H, s), 3.89(1H, dd, J=7.0 Hz,2.2 Hz), 4.0-4.3(1H, m), 4.66(1H, dd, J=7.9 Hz, 6.6 Hz), 5.5-5.7(1H, m),7.21(5H, s), 7.73(1H, d, J=3.3 Hz).

Example 10

Compound 8 was reacted with compound 12-B (i.e., compound 12 in which Yis a methoxycarbonyl group) in the same manner as described in Example9. Thus, compound 13-B (i.e., compound 13 in which Y is amethoxycarbonyl group) was obtained as an amorphous solid (in a 78.2%yield).

α!_(D) n.d.

¹ H-NMR (CDCl₃, δ): 0.7-1.1(m), 1.11(3H, d, J=7.0 Hz), 1.5-2.1(m),2.35(3H, s), 3.02(3H, s), 3.32(3H, s), 3.33(3H, s), 3.95(3H, s),3.8-4.3(m), 4.70(1H, dd, J=7.5 Hz, 6.8 Hz), 5.4-5.8 (1H, m), 7.23 (5H,s), 8.05 (1H, s).

Example 11

A 70% aqueous solution of ethylamine was added to 38.7 mg (47micromoles) of compound 13-B under cooling with ice. After completion ofthe dissolution, the resulting mixture was allowed to stand overnight atroom temperature and then evaporated to dryness under reduced pressure.The residue was purified by preparative TLC developing solvent:dichloromethane-methanol (10:1)! and then by Sephadex LH-20 columnchromatography using hexane-methanol-dichloromethane (4:5:15) as theeluent. Thus, 34.8 mg of the desired compound 13-C (i.e., compound 13 inwhich Y is an N-ethylcarbamoyl group) was obtained as an amorphous solid(in a 88.5% yield).

α!²⁸ _(D) -81.4° (c=0.309, MeOH)

¹ H-NMR (CDCl₃, δ): 0.7-1.1(m), 1.11(3H, d, J=7.3 Hz), 1.26(3H, t, J=7.3Hz), 1.5-2.2(m), 2.36(3H, s), 3.02(3H, s), 3.33(6H, s), 3.2-3.7(m),3.8-4.0(1H, br. dd), 4.0-4.3(m), 4.69(1H, dd, J=8.8 Hz, 6.8 Hz),5.3-5.7(1H, m), 7.24(5H, s), 7.95(1H, s).

We claim:
 1. A peptide compound of the formula ##STR15## or a saltthereof, wherein: (a) Q₁ represents a 1-dimethylamino-2-methylpropylgroup and Q₂ represents an (R)- or (S)-2-hydroxy-2-phenylethylaminogroup, a ² -phenylcyclopropylamino group or a1,2,3,4-tetrahydroisoquinolin-2-yl group, or(b) Q₁ represents a1-methyl-2-pyrrolidinyl group and Q₂ represents ##STR16## where A is ahydrogen atom or ##STR17## in which Y is a hydrogen atom or --COR₁, andR₁ is a hydroxyl group, a lower alkoxy group, an aralkyloxy group or##STR18## in which R₂ and R₃ are the same or different and are each ahydrogen atom, a lower alkyl group, a phenyl group, or a four- toseven-membered heterocyclic group having one or two heteroatoms selectedfrom S, O and N, or R₂ and R₃, together with the nitrogen atom to whichthey are attached, may form a four- to seven-membered heterocyclic groupwhich may further have one heteroatom selected from S, O and N, and B isa phenyl group which may optionally be substituted by a halogen atom,hydroxyl group, lower alkyl group or lower alkoxy group.
 2. A peptidecompound or a salt thereof as claimed in claim 1 wherein Q₁ represents a1-dimethylamino-2-methylpropyl group and Q₂ represents an (R)- or(S)-2-hydroxy-2-phenylethylamino group.
 3. A peptide compound on a saltthereof as claimed in claim 1 wherein Q₁ represents a1-methyl-2-pyrrolidinyl group and Q₂ represents ##STR19## where A is ahydrogen atom and B is a phenyl group which may optionally besubstituted by a halogen atom.
 4. A peptide compound or a salt thereofas claimed in claim 3 wherein the halogen atom is a fluorine atom.
 5. Apeptide compound or a salt thereof as claimed in claim 1 wherein Q₁represents a 1-methyl-2-pyrrolidinyl group and Q₂ represents ##STR20##where A is a 2-thiazolyl group which may optionally be substituted by anN-(lower alkyl)carbamoyl group and B is an unsubstituted phenyl group.6. A pharmaceutical composition comprising an effective amount of apeptide compound or a salt thereof as claimed in claim 1, and apharmaceutical acceptable additive.
 7. A method for treating a tumor ina patient which comprises administering an effective amount of a peptidecompound or a salt thereof as claimed in claim 1 to the patient.